The present invention relates to the manufacture of piezo-electrically active plastics film, commencing with the film material in its "raw" state.
One such material which may be used as the active element of an acoustic-electric transducer is polyvinylidene fluoride (PVDF), and the use of such active film materials in such a transducer is described in our British Application No. 7,903,224.
In making the diaphragm for such applications, it is necessary to apply electrodes to the two faces of the film material. This is usually performed by vacuum evaporation, which needs expensive equipment. Further, as the film has to be continuously polarized, the film is usually electroded over a large proportion of its surface area. However, when the material is to be used, e.g. in a transducer, it is often required that only isolated regions have to be electroded. Hence, the metallization has to be partly removed to give the required electrode shape, or the entire electrode must be removed and a new electrode of the required
The present invention seeks to overcome the above-mentioned disadvantages.